1. Field of the Invention
Exemplary embodiments of the present invention relate to a vibration insulator which insulates vibration at a portion where an air duct of a vehicle and a vehicle frame are coupled to each other; and, particularly, to a vibration insulator which is easily assembled and reduces a contact area where vibration is transmitted, thereby insulating vibration transmitted in a vertical direction.
2. Description of Related Art
In order to fix an air duct to a vehicle frame, a coupling bolt is used to fix an end of the air duct to the vehicle frame, and an insulating member is interposed at a contact portion between the coupling bolt and the air duct. The air duct serves as a path for supplying air to an engine of the vehicle from the atmosphere.
For example, referring to FIG. 1, as the coupling bolt 120 is coupled to a coupling nut 3 fixed to the vehicle frame 1 through a flange 2a formed at an end of the air duct 2, the air duct 2 is coupled to the vehicle frame 1. Furthermore, in order to insulate vibration, a vibration insulating bush 130 serving as an insulating member is interposed between the coupling bolt 120 and the flange 2a. 
However, when the air duct 2 is fixed to the vehicle frame 1 in the above-described described manner, a tool T as illustrated in FIG. 2 must be used to couple the coupling bolt 120, and vibration may not be sufficiently insulated in a vertical direction.
FIG. 3 is a cross-sectional view of a conventional vibration insulator. FIG. 4 is a cross-sectional view of the conventional vibration insulator when vibration is transmitted upward. When vibration is transmitted upward, the vibration insulating bush 130 and the top surface of the flange 2a come in surface contact with each other in a belt shape with a predetermined width, as indicated by ‘A’ of FIG. 4.
FIG. 5 is a cross-sectional view of the conventional vibration insulator when vibration is transmitted downward. Even at this time, the vibration insulating bush 130 and the bottom surface of the flange 2a come in surface contact with each other as indicated by ‘B’ of FIG. 5.
As described above, when vibration is transmitted in the vertical direction, the vibration insulating bush 130 comes in surface contact with the top/bottom surface of the flange 2a. Therefore, the contact area between the vibration insulating bush 130 and the flange 2a increases.
With the increase of the contact area, a reaction force to the transmitted vibration increases. Accordingly, since the vibration insulating bush 130 formed of an elastic material becomes more solid than in the initial state, the vibration insulating bush 130 may not normally absorb the transmitted vibration. As a result, the vibration insulating characteristic may be degraded.
Furthermore, when the air duct 2 is fixed to the vehicle frame 1, the coupling bolt 120 is coupled to the coupling nut 3 previously-fixed to the vehicle frame 1 by the tool T in a state where a collar 110 and the vibration insulating bush 130 are coupled to the flange 2a. In this case, since the coupling bolt 120 is coupled to the coupling nut 3 previously-installed in the vehicle frame 1 by the tool T after the flange 2a, the collar 110, the vibration insulating bush 130, and the coupling bolt 120 are assembled in a state where they are not fixed, the assembling is not easy to perform.
Furthermore, depending on an assembly tolerance, interference may occur between the vehicle frame 1 and the air duct 2. When the vibration insulating bush 130 is used to couple the air duct 2 and the vehicle frame 1, the assembling may be performed at the maximum tolerances allowed for the respective parts. In this case, since the centers of the through-hole of the flange 2a, the vibration insulating bush 130, the collar 110, and the coupling bolt 120 are not aligned with each other, the respective parts may be assembled toward one side.
When the centers of the through-hole 2b of the flange 2a, the vibration insulating bush 130, the collar 110, and the coupling bolt 120 are not aligned with each other, vibration may not be effectively transmitted. Furthermore, when the engine is driven, the vehicle frame and the air duct may interfere with each other.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.